When Death Comes Knocking
by Goldenbrook15
Summary: The day that Tadashi lost his brother in the school fire was the day that he lost his happiness. Nothing would be the same again . . .
1. grief

**Disclaimer: I do not own Big Hero 6.**

 **I needed to post something. I just went through a life shattering experience for the first time in years (not the good kind) and it's shaken me. I don't have a completed chapter for any of my other stories so I decided to finally put this up. Enjoy and please leave a review.**

 **When Death Comes Knocking**

 **Chapter One**

 _Grief_

 _It's all my fault . . ._

Tadashi clutched the slightly singed ball cap in his hands, staring blankly at the red box that held his latest creation. He had built it for Hiro because his little brother couldn't seem to keep himself from getting hurt. It had taken him years of research. He'd been planning to show it to the kid . . . but his brother would never get the chance to see it.

Because he was dead. Gone. He wasn't coming back.

 _If I hadn't pushed him to attend my school this wouldn't have happened._

He hadn't expected it. There was no warning, no last good-by. One moment he was there, standing beside him and the next . . . the next Tadashi realized that he would never see him again, because the fire _took him._

 _Just like it took mom and dad._

The fire had stolen his parents, and now it had ripped his brother from him too, the brother he had promised to protect, all those years ago. The brother he had failed to save.

 _All my fault._

The hat twisted in his hand, wrinkling and stretching. Then, so suddenly that it made him jump, the strong material ripped. Tadashi stared down at the hat blankly, turning it slowly to see the front, where the logo for his school was now torn in half, ruined.

Just like his school had been ruined.

Tadashi tried to hold it in, he really did, but the sob slipped from him before he could contain it. He blinked tears from his eyes, more sobs forcing their way after the first as he pulled the hat to his chest. Gasping breaths pulled air into his burning lungs only for it to get stolen away again and again.

Doubling over and shoving his head into his pillow Tadashi cried for the first time since his parents died. He cried for his parents, for Hiro, for the life his little brother would never get to have.

He cried until he could cry no more and then fell into an uneasy, exhausted sleep where his dreams tortured him with the image of the smiling face of his brother going up in flames.

 _I'm so sorry, Hiro._

0~o~0

 _They laughed as they walked out of the school campus and Tadashi reached out to ruffle his brother's hair._

 _"Did you see that!?" Hero laughed, dodging out of reach and nearly skipping ahead, "Did you see there faces? They_ totally _weren't expecting that!"_

 _Tadashi smiled fondly. "You were amazing Hiro."_

 _Hiro grinned back at him. "So, where are we going to celebrate?"_

 _Shrugging and shivering ever so slightly as the wind blew past him Tadashi replied, "You might want to tell Aunt Cass first."_

 _"Oh, right! We haven't told her what I've been working on yet! She'll be so excited when I show her . . ." he paused as he touched the top of his head only to find the thin band that had encircled his head was gone. Groaning softly Hiro turned to Tadashi and sighed, "I must have left the nano-transmitter back in the school."_

 _Tadashi laughed and shook his head. "Go grab it. I'll wait right here till you get back."_

 _The grin was back on Hiro's face. "Thank's Tadashi," he chirped and then dashed back toward the entrance._

 _Tadashi watched him slip through the doors and couldn't help but feel a shiver of fear go up his spine. Most of the people had already left and there were only a few stranglers for now. Shrugging the feeling off he turned as he saw his lab friends making their way toward him._

 _"That was_ wicked _!" Fred shouted, pumping his fist in the air and drawing strange looks from the people around him, "Hiro completely floored them!"_

 _"Speaking of the squirt," Gogo popped the bubblegum she had been blowing, "where is he?"_

 _Joining his friends as they drifted away from the school slightly and toward the front lawn, just out of sight of the entrance, Tadashi answered, "He went back to grab the controller."_

 _Wasabi nodded knowingly, "Good thinking. You don't want to leave that kind of stuff lying around."_

 _Tadashi laughed and tried to force the foreboding back down again. "I'm sure that wouldn't happen. At a convention like this there are probably lots of guards making sure nothing gets stolen."_

 _Wasabi shrugged. "You never know."_

 _"Hey, guys," Honey Lemon suddenly spoke up, her gaze focused back toward the school, "Why are there people running_ out _of the building."_

 _Fear flooding back, Tadashi shot up from his sitting position on the grass – when had they sat down? – and looked back the way they had come. Sure enough, the last of the people were running from the building and behind them a wall of flames lit up the inside of the school._

 _"Hiro!" the cry was past Tadashi's mouth before it even made it to his brain and he was already rushing forward. Now that he knew what was happening, he could hear the distinct crackling of fire, oh so familiar. "Hiro, where are you?!"_

 _Please have made it out. Please have made it out already . . ._

 _"Hiro!" he searched the crowed but the distinct thin, black haired boy was nowhere to be seen. Catching a lady that looked vaguely familiar on the arm as she rushed past he quickly gasped out, "Did everyone make it out?"_

 _She shook her head and looked back at the building. "Professor Callaghan is still in there."_

 _"What about a kid, about fourteen years old, black hair, and gave a presentation?"_

 _She shook her head again, turning back to him, "I . . . I don't know . . ."_

 _Letting her go Tadashi dashed to the steps. If there was even a chance that his brother was in that raging inferno he knew that he had to go in. He couldn't leave his brother alone. Not again._

 _Half way up the staircase Tadashi spotted Hiro staggering forward out of the fire, coughing and pulling his shirt up over his mouth._

 _"Hiro!" Tadashi ran forward, reaching toward his brother, who was still far from the entrance of building, as if he could pull him the last couple of yards._

 _The flames flared upward and Hiro's eyes widened as he glanced behind him in fear. Tadashi couldn't see what he was looking at and didn't particularly care as he tried to find a way around the flames._

 _"Hiro! Can you-" his sentence was broken off by an explosion. In his shock he felt the warm air and fire slam into him, sending him flying backwards. His head hit the pavement with a loud crunch and his vision wavered._

 _The last thing he saw before everything went black was his cap fluttering to the ground and the building collapsing in on itself._

0~o~0

Tadashi slammed the helmet on his head and kicked off from the curb, roaring away into the night on his motorbike, not seeing the sad gaze of his aunt watching him go.

The bike squealed around the turns at a much faster speed than they should probably be taken but Tadashi didn't care. If he died at that moment he would have actually been grateful, anything that would help him to escape from this world that haunted him with reminders.

 _Hiro's_ bed was empty, his workspace too clean. There were no bits and peaces scattered around to pick up and, when Tadashi woke up in the middle of the night, there was no brother willing to listen to him and talk him back to sleep after a nightmare.

Another turn left black skid marks of the faded road.

He just had to get away for a little bit.

Hiro and Cass had been his whole world, ever since his parents died. Friends were great and all but they could only help so much. And now . . . now one of his anchors was gone, just like his parents.

Tadashi let out a yell of anger and jerked his handlebars around another corner, but this time he _was_ going too fast and his bike tipped on its side and started to skid, Tadashi kicking away just in time. The bike slammed into the side of a large, abandoned storage house and shattered the rotting planks.

Groaning, Tadashi rolled onto his back and stared up at the sky. Typical for the city the glow from traffic and other lights blocked out the stars, leaving it a blank canvas of darkness. Once again he felt tears seep out of the corners of his eyes and he closed them, feeling his breath hitch.

 _This isn't what Hiro would want_.

Tadashi knew that, but for the moment he wanted to grieve. He wanted to remember the brother that he loved so much without the regret of creating the events that lead to his death.

 _If only –_

Something rattled and Tadashi jerked upward into a sitting position, grabbing his arm with a hiss as the bruised shoulder was jostled. Glancing around and not seeing anyone, nor recognizing where he was, he struggled to his feet and backed toward his bike.

There was another rattle, this time from behind him, and Tadashi spun around, looking at the hole that his bike had created in the side of the building. From the shadows something moved and his eyes fixed on it, only for him to freeze.

 _What in the –_

A microbot, one that looked _exactly_ like the ones he had helped Hiro create, rolled sluggishly along the ground toward the abandoned building. Breath coming quicker Tadashi reached down and grabbed the lone bot, holding it in his hands as he gazed into the darkness. Biting his lip, he contemplated what to do.

On one hand, these were supposed to have been destroyed . . . on the other, no one but he and Hiro knew how to make them. He had seen Hiro die. So who . . .

From within the darkness there was another shift and Tadashi made his decision as he felt the bot in his hand nudge forward. Darting into the hole and blinking his eyes to adjust he just barely held back a gasp at what he saw.

Microbots. There were hundreds of them popping out of machines and into barrels one by one. What had started as a few garbage cans was now an army. And, behind it all, a tall man stood in completely black clothing. Except for the white mask that hid his face, there was no color against the black, _moving,_ backdrop.

The mask moved, the man behind it looking up, and Tadashi didn't stick around to see what would happen. Grabbing his bike he dove back out of the hole and hopped on. He started it and kicked off just as a black swarm of technology stabbed at the place he had been.

Speeding away, Tadashi only had one thought on his mind.

 _The fire wasn't and accident . . . someone_ murdered _my brother._

 **0~o~0**

 **Please review. I'm feeling kind of down on life . . .**

 **(Updated 10/4/2016)**


	2. To Late to Turn Back

**Disclaimer: I do not own Big Hero 6.**

 **I have everything for this story planned out . . . but this chapter didn't want to cooperate. If it feels like a filler, sorry. It will start picking up in the next chapter. This is mostly just more of Tadashi working through his grief and how deeply Hiro's death has effected him. Oh, but there is a surprise visit near the end. Enjoy!**

 **When Death Comes Knocking**

 **Chapter Two**

 _Too Late to Turn Back_

The bike screeched to a stop and Tadashi let it drop loudly to the ground as the stepped off, his breathing irregular. One hand was clutched over his beating heart as he tried to force air back into his lungs even as the panic threatened to overtake him. His other hand trembled from its position on the wall and his legs felt like jelly.

 _I have to get to the police. They –_

 _No. We never reported the microbots as missing. Who would? There was a fire! It would have destroyed all of the evidence! The police won't believe me if I tell them . . ._

 _What about my friends –_

 _I . . . I can't tell them. They won't understand; they_ don't _understand . . ._

 _I can't tell anyone . . . I'm alone._

A sob forced its way from his throat.

 _No parents, no brother, no friends. It's just me._

His legs collapsed under him and he slid down the side of the wall, looking blankly out toward the docks that he was facing.

 _It's all my fault._

He stayed in that position well after midnight, never noticing when his tear tracked cheeks relaxed and his blank eyes closed in sleep.

 _I'm so sorry, Hiro._

0~o~0

It was morning by the time Tadashi managed to pull himself out of his misery enough to go home. Aunt Cass didn't question him as he stumbled up the stairs, silently taking note of his dark eyes and numerous scraps. He knew that she worried about him but he couldn't bring himself to comfort her when he couldn't even do that himself.

His bed was unmade, the area around it littered with broken inventions and crumbled papers. Tadashi just shoved them to the side with his foot as he crumbled into his bed, ignoring the empty other side of the room. He stared blankly at his white wall, feeling numb.

After his breakdown out on the streets Tadashi hadn't known what to do. There wasn't anything that he _could_ do. He was an inventor, not an investigator or a police officer. What could he do against a man who _murdered_ his brother for the invention that _he_ helped Hiro create?

Tadashi was too exhausted to even cry.

The world seemed to swirl around him, completely devoid of color and feeling.

What was the point? Hiro was gone. Even if he did catch the masked man, it wouldn't bring Hiro back. It wouldn't save his brother.

Tadashi closed his eyes, silent sobs rattling his frame as he shuttered on the bed.

Maybe it would have been better if _he_ were the one that had died in that explosion.

Aunt Cass slipped out of the room silently, taking the uneaten plate of food with her. She didn't lift her eyes from the floor as she left, unnoticed.

0~o~0

Gogo popped her gum loudly, relishing in the slight flinch of her history teacher at the loud noise. He gave her a glare in warning but didn't say anything, like always. Her eyes flickered to the clock hanging on the wall with boredom, silently wondering when the class would end.

It had been two weeks since the funeral for Tadashi's brother and Professor Callahan. She hadn't seen Tadashi since then and she was starting to get worried about him. The other science nerd _never_ missed class. Of course, that was before the fire.

Now, though, Gogo was seriously wondering if she should go slap her friend out of his grief. Knowing him, he would do something drastic if someone wasn't watching him, and she didn't want that to happen. Tadashi needed them to help him, but he had started to withdraw and it wasn't a good sign.

 _Tick, tock, tick, tock, tick . . ._

Gogo nearly growled in frustration as she looked at the clock. She sucked in a deep breath and then started to blow back out again. The pink bubble started expanding and then . . . _Pop_!

Another flinch from the professor.

The flattened bubble quickly disappeared back into her mouth as she started to breath in again.

"All right class," the professor shouted suddenly and clapped his hands - his eyes darted in her direction nervously - and startling several of the students from slumber, "Class is over for the day. Don't forget the essay due next week!"

Gogo go was already half way out of the door by the time he was done talking.

 _I hope Tadashi appreciates this._

0~o~0

Deep in the underground of the bustling city a man stared into the dark pits of the porcelain mask's eyes. His own were dull and lost in thought. Dark, grim ridden clothing hung from his large frame, giving him an intimidating air even as he sat among the street rats and abandoned garbage.

 _Fire. Bright, angry fire roared around him as he settled the band around his forehead, breathing deeply. Finally, this was his chance. His chance for revenge._

 _He turned around, small bots pouring from their hiding places to surround and protect him. His feet walked confidently through the flames, untouchable, invincible, unchallenged-_

 _"Help!"_

 _The young voice made him pause, wavering slightly. Hadn't everyone else made it out? He'd been sure to check first . . ._

 _"Someone? Anyone! Please!" the person broke off in a deep, lung rattling cough, "H-help!"_

 _He could see them now, a shadow among the flames. Wavering, he debated over the consequences. He could safe the boy . . . but then everything would be revealed. He couldn't do that, not after everything that he had been through._

 _"P-please," the boy stumbled toward the exit. He could see it from the corner of his eyes. And then the kid turned toward him, and he knew exactly who it was._

 _Wide, brown eyes, filled with youth and innocence. A prodigy in the making. Hiro._

 _The boy's eyes widened, filled with fear as he saw his own invention swarming around the elder man. Then something clicked and his eyes widened in understanding, in horror. Hiro ran._

 _And the roof collapsed on top of his small frame, forever lost to the flames._

"I never meant for this to happen, you know," he whispered quietly, "No one else was supposed to get hurt."

 _Tadashi's eyes widened as he saw the mass of black came hurtling toward him, barely managing to escape certain death._

"I'm so sorry Abigail."

His eyes hardened. Thoughts of the past, the present, and the ruined future crowding for attention.

"I can't turn back now."

The mask slipped over his face and he stood up, walking deeper into the darkness. With a near silent rattle the black of night seemed to swallow him whole.

0~o~0

 **Hey. I want to thank everyone who reviewed on the last chapter. If you read the author notes you probably know that I was going through a hard time. I am feeling a little better now and I want to thank you all for your encouragement and support. I really hope that you liked this chapter. It didn't get into the good stuff yet, but I couldn't find a way to fit it into this chapter. In fact, this got rewritten so many times that it is not even funny.**

 **I really hope that you all liked it. Oh, and how would you all like a "cut scenes" at the end of the story of everything that I wanted to put in but that would not fit? Let me know.**

 **Reviews?**

 **(Updated: 12/31/2016)**

 **Happy New Years!**


	3. Armor

**Disclaimer: I do not own Big Hero 6.**

 **Please tell me what you like and what I can improve on!**

 **When Death Comes Knocking**

 **Chapter 3**

 ** _Armor_**

"Tadashi!" the loud banging against his locked door didn't even jar him from his work as he scanned over the notes that he had been compiling, trying to make sense of what he had seen and heard in that old warehouse. Dark circles hung from his eyes and his hair was undone with messy streaks of oil through it. "Tadashi, if you don't open the door this instant I will _break it down!"_

Tadashi paused. That wasn't Aunt Cass. His eyes widened as he frantically gathered all of his papers and stuffed then under his bed along with an abandoned pizza box. He didn't even cringe as he picked his way through the garbage and discarded papers that he hadn't bothered to pick up in the last week or two.

"Tadashi! I'm warning you! If you don't-!" Gogo's voice growled from behind the locked, flimsy door and Tadashi yanked it open, a scowl firmly in place.

Gogo cut off and leaned back, wrinkling her nose. All of his friends behind her had a similar reaction to the smell that rolled off of him waves. Of course, he hadn't taken a shower since the _incident_ . . . the smell was sure to linger.

"What do you want?" his voice came out horse and defeated, surprising him. He looked over the group in confusion. Why were they here? Not that he didn't like seeing them or anything but, well, he had things to do and they knew that he didn't like being interrupted when he worked . . .

"Tadashi," Honey Lemon looked on the brink of tears as she looked at his wrinkled appearance, "We came to see if you were ok. School started two weeks ago and, well, we haven't seen you there so . . ."

 _Why would I go?_ He nearly growled, but withheld it, _Hiro's not going to be there._

"Leave," he demanded, his face hardening.

"But, Tadashi-"

 _"Leave,"_ he repeated, more forcefully, anger bubbling up inside of him as he clenched his fists until the handle creaked under his white knuckled grip, "I _don't want to hear it_. I _don't care_ if you say that it's going to be alright _because it's not_. Hiro is _gone_ and _he's not coming back_ so don't tell me to _get over it."_ The last few words came out wobbly and he was horrified to realize that tears were gathering in his eyes.

"Oh, Tadashi," Honey Lemon's eyes were wide and she looked conflicted, "I . . ."

Tadashi braced himself for the onslaughts of meaningless ' _I'm sorry's_ but, to his surprise he found a pare of arms around him. He blinked as he looked down and saw Honey's bright blond hair buried in his chest. A quick glance upward showed that Gogo, usually emotionless, looked seconds away from following her. If Fred hadn't been in the back he was sure that the superhero geek would have joined in already.

Slowly, Tadashi wrapped his arms around Honey Lemon as she began to sob into his shirt, leaving a wet patch on the grey fabric. At his stunned expression Gogo scowled.

"What, did you think that we were just going to let you sit around and mope!?" she snapped angrily. "Hiro wouldn't want that! His brother is strong; he wouldn't have just _given up_! So _where are you, Tadashi?_!"

Honey Lemon's tears decreased but she didn't pull away.

"I . . ." Tadashi didn't know what to say. He glanced over all of them, taking in their worried faces. "I . . ."

" _You,_ " Gogo stressed and Honey Lemon pulled away to see his reaction, "are coming with us and _we_ are going out to the memorial."

Tadashi blinked. "What . . ."

 _"Now."_

Five minutes later Tadashi found himself being chased out of his own home, mildly wondering if he was hallucinating.

0~o~0

"And do you remember that time when Hiro set Mega Bot on Fed because he wouldn't stop bugging him for a flamethrower? Priceless!" Honey Lemon said while laughing and holding a warm cup of chocolate milk in her hand.

Tadashi smiled softly as he took a sip of his own chocolate, lost in his memories. They'd just come back from the memorial for his little brother and while he couldn't say that he was content some of his deep set sorrow had cleared. He didn't feel like laughing, but neither was he about to burst into tears.

In the back of his mind the haunting mask remained to taunt him.

"I _would_ have asked for a super-flaming-lizard-suit," Fred grumbled with mirth filled eyes, "But _someone_ kept saying that it was impossible." His words were emphasized by a glare toward Gogo, who simply let her gum pop loudly with a dead look of boredom.

"A super-flaming-lizard-suit is _not_ science, Fred," she drawled emotionlessly.

"Of course it is!" Fred grabbed a random cup of chocolate – his own sadly empty – and chugged it down, ignoring Wasabi's horrified face as his cup became contaminated by Fred Germs, "Haven't you ever seen any of those _Science_ fiction movies?"

"Yah, well, that's not really _Science_ either-"

The conversation continued, no one noticing the way that Tadashi suddenly froze in his seat, cup paused half way to his mouth.

Super-flaming-lizard-suit.

Super-suit.

Super-Hero.

Super _powers._

 _Super villain._

The guy in the mask used Hiro's Microbots to enhance himself, to be able to do things that a normal human couldn't do. And he was using his powers for evil, which according to all of the comics that he'd ever read, made him the bad guy.

 _And where there are villains, heroes will rise._

Tadashi clenched his cup tightly.

 _But . . . I'm no superhero. I don't have any extra powers and even_ if _I built a suit to help me I couldn't do anything against an army of Microbots . . . could I?_

Quietly Tadashi stood and left, his friends too engrossed in their conversation to see that he'd left. Even Gogo didn't realize he was gone until they were all ready to go home for the night. Silently, she wondered what had made him leave.

Hiro's death changed Tadashi so much . . . and she still wasn't sure if it was a good thing.

0~o~0

Tadashi squeezed his eyes shut, trying to keep himself awake as he scribbled down ideas. His desk looked like a miniature tornado had struck it, whipping paper everywhere. Sketches of machine parts, complicated theories, and plans lay crumbled everywhere.

 _Fire? No, the bots would have to be superheated in order to melt, and I didn't have anything that could do that fast enough to not get caught._

 _Strength Boost? No, no point. The bots are small, they would simply bend around all attacks._

 _Water . . . not solid enough._

 _But what about . . . Ice?_

Tadashi paused, his eyes blank as he thought for a moment.

 _Ice . . . its hard enough to hold the Microbots in place and easy to create. I can also target it at specific points._

His pencil tapped against the surface and a slow smile stretched across his lips, slightly hysterical.

"That . . . that might just work!"

 **0~o~0**

 **I hope that you all liked it!**

 **On another note, I am going to be leaving FanFiction soon. I will try to finish all of my published stories, but my unposted ideas are up for adoption on my profile if anyone wants to go look at them.**

 **Review? Please?**

 **(Updated: 3/21/17)**


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